The parietal lobe contains the somatosensory cortex (see ) and the adjacent parietal association cortex. The parietal association cortex gets information from somatosensory, visual, and auditory cortices and is involved in the processing, perception, and integration of sensory information. Connections with the frontal lobe allow somatosensory information to aid in voluntary motor activity. Somatosensory, visual, and auditory information can also be transferred to language centers, such as Wernicke’s area, as described later. Lesions in the left parietal lobe can result in Gerstmann’s syndrome, which includes a person’s inability to name his or her fingers (or those of another) and a loss of the ability to perform numerical calculations. The right parietal lobe is involved in determining spatial context. Localized lesions can result in the neglect syndrome, in which the patient seems unaware of the left side of his or her body and of persons, objects, and events on his or her left. (See an “
In the Clinic ” box later in this chapter.)
The major function of the occipital lobe is visual processing and perception (see ). The primary visual cortex (Brodmann area 17) lines the calcarine sulcus and is flanked by secondary (Brodmann area 18) and tertiary (Brodmann area 19) visual cortices. Lesions of these areas in the cuneus gyrus result in blindness in the lower contralateral visual field; those in the lingual gyrus result in blindness in the upper contralateral visual field. Connections to the frontal eye fields affect direction of gaze, and projections to the midbrain assists in the control of convergent eye
Twoareasimportantforplanningandexecutingmotortasksaretheparietal cortex andthefrontal cortex, theformerbecauseitintegratessensoryinformationneededtodefinethecontextofatask(see ).Mirrorneuronshavebeenfoundinboththeinferior parietal andtheinferior frontal cortices of macaques. Thesecellsrespondduringperformanceofaspecificmotortaskandalsoduringobservationofthesametaskperformedbyanotheranimal.Becausethesemirrorcellsseemtoencodeforandrespondtoveryspecificandparticulartasks,ithasbeenspeculatedthattheymayunderliesuchfunctionsasunderstandingtheintentionsofothersandempathy,aswellastheabilitytolearntasksfromobservation.Inhumans,EEGactivityconsistentwiththebehaviorofsuchmirrorneuronshasbeenlocalizedtotheinferior frontal andsuperior parietal lobes. Autism,whichinvolvesaninabilityto“read”theintentionsandemotionsofothers,hasbeenlinkedtoalackofmirrorneuronsbyEEGevidence.
movements, pupillary constriction, and accommodation, all of which occur when the eyes adjust for near vision.
The temporal lobe has many different functions, including the processing and perception of sounds and vestibular information and higher order visual processing (see ). For example, the infratemporal cortex, on its inferior surface, is involved in the recognition of faces. In addition, Meyer’s loop, which forms part of the optic pathway, passes through the temporal lobe. As a result, temporal lobe lesions can damage vision in upper part of the visual field. Similarly, a portion of Wernicke’s area, essential for the understanding of language, lies in the posterior region of the temporal lobe.
The limbic system dominates the medial temporal lobe (see
Fig. 10.4 ), and it participates in emotional behavior and in learning and memory (see the “Learning and Memory” section). The limbic system helps control emotional behavior, in part by an influence on the hypothalamus via the Papez circuit. This circuit projects from the cingulate gyrus to the entorhinal cortex and hippocampus, and from there, via the fornix, to the mammillary bodies in the hypothalamus. The mammillothalamic tract then connects the hypothalamus with the anterior thalamic nuclei, which project back to the cingulate gyrus (see